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List:       gcc-patches
Subject:    Re: [patch] cse.c: Speed up delete_trivially_dead_insns.
From:       Jeffrey A Law <law () redhat ! com>
Date:       2005-01-31 22:26:19
Message-ID: 1107210379.4463.64.camel () localhost ! localdomain
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On Mon, 2005-01-31 at 08:30 -0500, Kazu Hirata wrote:
> Hi,
> 
> Attached is a patch to speed up delete_trivially_dead_insns by not
> iterating.
> 
> On mainline, we do a lot of work on constant propagation, DCE, and DOM
> among other things, so delete_trivially_dead_insns does not have as
> many opportunities to remove insns.  Here are some numbers obtained
> while compiling cc1-i files.
[ ... ]
Approved.

FWIW, I can speculate on ways to get dead code past the SSA optimizers
in such a way as to require iteration from delete_trivially_dead_insns.
However, they would be pretty convoluted testcases.  I suspect that such
code is already exceedingly rare in practice and will only become rarer
still as the SSA optimizers continue to improve.

Jeff


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